Hydrogen Evolution from Aqueous Solutions Mediated by a Heterogenized [NiFe]-Hydrogenase Model: Low pH Enables Catalysis through an Enzyme-Relevant Mechanism

[NiFe]-hydrogenase enzymes are efficient catalysts for H-2 evolution but their synthetic models have not been reported to be active under aqueous conditions so far. Here we show that a close model of the [NiFe]-hydrogenase active site can work as a very active and stable heterogeneous H-2 evolution catalyst under mildly acidic aqueous conditions. Entry in catalysis is a (NiFeII)-Fe-I complex, with electronic structure analogous to the Ni-L state of the enzyme, corroborating the mechanism modification recently proposed for [NiFe]-hydrogenases.